1. Field of the Invention
This invention relates to improvements in multistation sheet metal transfer press equipment, and more particularly to so-called eyelet presses adapted to blank out and then progressively form relatively small to medium sized parts from strips of sheet metal stock.
2. Discussion of the Prior Art
Multiple station metal stamping apparatus has long been used in the mass production of a wide variety of metal parts. In general the apparatus is adapted to stamp a blank or disc-like piece from a strip of sheet metal stock introduced at a first station of the press, and to advance the resulting piece through a succession of shaping or forming operations, in stepwise manner at sequential forming stations arranged along a press bed. One type of transfer press commercially available employs a driveshaft about which a plurality of cams is angularly secured to cooperate with adjustable cam followers, the several cams being located at respective forming stations of the press. Punch members of tool and die sets at each of the forming stations are reciprocated by the cams with each revolution of the driveshaft to provide the punching or drawing operation on the workpieces. Transfer mechanism on the press bed is provided to advance the workpieces stepwise through the various tool stations to a point of discharge. Presses of this type are shown in U.S. Pat. Nos. 3,369,387 and 3,683,665, for example.
In another type of commercially available press, all of the punches of the several tool and die sets are mounted to be operated simultaneously by a single horizontally disposed heavy ram. This is reciprocated vertically by matched precision-ground cams engaging opposite ends of the ram to raise and lower it with each revolution of the driveshaft by which the cams are driven. Again the reciprocating motion is used to operate the punches of the tool sets at each station of the press. This form of press is shown for example in U.S. Pat. Nos. 2,049,915 and 4,166,372. The invention here is designed more particularly for use in the latter type of press.
Various modifications of these transfer presses have been developed by the trade in terms of how the sheet metal feed stock is fed to and the workpieces are progressed through the forming stations. Such modifications include arrangements in which dual strips are fed first to duplicate blanking stations, and the workpieces are then transferred, pair-wise, from one station to the next. In U.S. Pat. No. 3,369,387 mentioned above, the duplicate stations are paired on opposite sides of a central transverse plane of the press, with the feed stock entering at opposite ends of the press, while the workpiece forming operations progress inwardly toward that central plane to discharge the finished product at that point. In U.S. Pat. No. 3,683,665, also mentioned above, the sheet stock material is fed centrally of the tool line in the press (i.e., at the central transverse plane), and duplicate blanks punched from the strips at the first pair of stations are then transferred pair-wise but in opposite directions outwardly from that central plane through the several paired tool stations toward opposite ends of the press. That is, in this type of press, the duplicate stations are paired so as to be equidistant from but on opposite sides of that central plane.
In U.S. Pat. Nos. 3,461,708 and 3,650,141, the presses illustrated embody duplicate sets of forming tools, but these are paired in adjacent sets transversely of the direction of workpiece travel, rather than longitudinally of it as in the patents just mentioned. That is, they are paired across a vertical plane running longitudinally of the press bed. Similarly, U.S. Pat. No. 3,800,583 shows an arrangement of duplicate tool sets in which the tools at each station are paired transversely of the workpiece travel, similar to the arrangement in the last-mentioned patents but incorporating the center fed arrangement of a machine such as that shown in U.S. Pat. No. 3,683,665.
While this prior art shows double-feed arrangements for punch and draw work, none of it mentions roll forming.